Such clamp systems or snap-fit couplings enable a rapid and reliable connection to gas bottles for example, so that time-consuming screwing on and unscrewing at the connection counterpiece is eliminated. The clamping jaws suspended in a clamp piston thus engage positively in internal and external threads, collar nozzle and flange connections etc. Furthermore, such clamp systems or snap-fit couplings as a rule have a spreader mandrel, about which the clamping jaws are located at the forward end of the structure, the clamping jaw arrangement coupled to the actuating device being movable relative to the spreader mandrel in the axial direction, in order in this way to bring the clamping jaws into the engagement position or to disengage them from a connection counterpiece. Thus the clamping jaws project with their forward connection ends beyond the forward edge of the spreader mandrel and are pressed together for example by means of a resilient O-ring located around them in such a way that the clamping jaws are radially pivoted and the snap-fit couplings can be inserted into the connection counterpiece. Renewed actuation of the actuating device causes a renewed axial displacement of the clamping jaw arrangement relative to the spreader mandrel, but in the direction into the casing, so that the clamping jaws are radially spread by the spreader mandrel and the clamping jaws pass into secure and reliable engagement with the connection counterpiece.
A disadvantage of such a structure is however that the clamping jaws, seen in the peripheral direction, are displaceable radially to one another. In this way engagement profiles are formed which, depending on the degree of the radial spacing of the clamping jaws from one another, form an engagement profile which deviates more or less from the engagement profile of the connection counterpiece. For example, by means of a snap-fit coupling with six clamping jaws, which are intended to engage in a circular connection of a counterpiece, by a radial arrangement of the clamping jaws, in which not all the clamping jaws have the same or roughly the same spacing from one another, an engagement profile can only be formed which is not entirely circular. Upon connection to the counterpiece of a gas bottle for example, therefore due to the imprecisely-fitting connections, tilting due to non-uniform support can occur, which can result both in increased wear on material and a lack of seal of the connection. In addition the clamp system, due to the spreader mandrel mounted on the rear portion of the casing, is relatively long.